This enables consumer projects to call find_package(dasi) ...

Adds C API example "weather".

Start porting C API from old-develop branch.

Fix missing includes and namespace issues in various files.

When debug is on, print schema path before fdb.archive()

Start merging RetrieveResult and add missing methods.

Prints out;
- schema rules as query string,
- all data in all root paths.

…ured directories